Namespaces
Variants

std::forward_list<T,Allocator>:: empty

From cppreference.net

C++
Containers library
std::forward_list
Member functions
Non-member functions
(until C++20) (until C++20) (until C++20) (until C++20) (until C++20)
Deduction guides (C++17)
bool empty ( ) const noexcept ;
(since C++11)
(constexpr since C++26)

Checks if the container has no elements.

Contents

Return value

true if the container is empty, false otherwise.

Complexity

Constant.

Example

The following code uses empty to check if a std:: forward_list < int > contains any elements:

Run this code 
#include <forward_list>
#include <iostream>
int main()
{
    std::forward_list<int> numbers;
    std::cout << std::boolalpha;
    std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';
    numbers.push_front(42);
    numbers.push_front(13317); 
    std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
}

Output: 

Initially, numbers.empty(): true
After adding elements, numbers.empty(): false

See also

returns the distance between two iterators
(function template)